Activated carbon has been used as a purification agent since Roman times. Carbon treatment is based primarily on a naturally occurring phenomenon called adsorption, wherein molecules of a liquid or gas are trapped by either an internal or external surface of a solid. Activated carbon has a high internal surface area, and is therefore a suitable material for adsorption applications.
Activated carbon can be manufactured from a wide variety of raw materials, and by controlling the creation of the active surface of the carbon particles by carefully selecting and implementing a combination of chemical, mechanical, and thermal processing stages, activated carbon materials designed for specific purification applications are achievable.
Sodium xylene sulfonate is one of a group of compounds known as alkyl aryl sulfonates, and is a commonly used hydrotrope in the consumer products industry. A hydrotrope is a compound that has the ability to enhance the water solubility of other compounds. Some specific examples of hydrotropes include, but are not limited to, sodium cumene sulfonate, ammonium cumene sulfonate, ammonium xylene sulfonate, potassium toluene sulfonate, sodium toluene sulfonate, sodium xylene sulfonate, toluene sulfonic acid, and xylene sulfonic acid. Other useful hydrotropes include sodium polynaphthalene sulfonate, sodium polystyrene sulfonate, sodium methyl naphthalene sulfonate, and disodium succinate.
During the manufacture of hydrotropic compounds, as with most chemical manufacturing processes, it is typical for the final reaction product to comprise not only the desired hydrotropic compound, but also small amounts of unreacted reagents, contaminants, and/or one or more reaction byproducts. In some instances, these unreacted reagents, contaminants, and/or reaction byproducts can be odoriferous, and thus can impart an odor to the final reaction product. For example, residual odoriferous compounds often encountered in connection with the above-listed hydrotropes include xylene, cresol, toluene, cumene, polystyrene, styrene, naphthalene, polynaphthalene, and other compounds. Although such odoriferous compounds typically are present in amounts insufficient to affect the efficacy of the hydrotrope in the end product in which it is used, the odors they impart may be undesirable for some applications. For example, when hydrotropes are employed in consumer product formulations, such as personal care products, it is generally desirable for them not to impart an odor to the resultant formulation, as such an odor may need to be countered with fragrance additives. And indeed, in the formulation of “fragrance-free” products, it is most desirable for the components of the formulations to not impart odors that ultimately must be neutralized in some way.
In the case of the hydrotrope sodium xylene sulfonate, for example, it is common for odoriferous compounds such as xylene and cresol to remain in solution with the sodium xylene sulfonate during manufacture. Although manufacturers and consumers of sodium xylene sulfonate have attempted to reduce and/or eliminate the malodors imparted by these compounds from sodium xylene sulfonate compositions, to date, no effective materials or methods have been identified for this purpose.
Thus, a method is needed to reduce the level of odoriferous compounds in hydrotropic compositions and thus improve the detectable residual odor of such compositions. It is desired to address these issues without increasing the manufacturing costs and/or processing complexity of such hydrotropic compositions and/or the product formulations that utilize these compositions.